Fore and aft rigged sail boats quite typically employ a multiple sail configuration for improving efficiency and performance when going to windward. A typical Bermuda-rigged sloop, for example, employs a main sail and jib, with the two sails being trimmed in concert in a manner that each enhances the performance of the other.
Notwithstanding the superior windward performance of the Bermuda rig, for example, many sailing vessels, such as cat-rigged sloops, ketches and schooners, utilize mast-mounted sails without jibs. Such vessels, at a sacrifice to windward ability, have advantages of convenience and in many cases have superior off-wind performance.
It is generally believed that the superior windward performance of a Bermuda rig, for example, is derived from the slot-forming effect of the jib, in association with the main sail. It is accordingly a feature of the invention to provide a novel and improved slot-forming foil device, for use on cat-rigged and similar vessels employing no jib, for the purpose of providing a slot effect, similar to that provided by a jib, but without the cost, structural loading, and handling complications of a conventional jib. It is known, in for example, the Latham U.S. Pat. No. 4,437,426 to provide a slat-like device immediately in advance of a single sail, in order to provide a slot effect and thereby to enhance the performance of the single sail. The slat device of the Latham patent is a freely pivoted, self-tending element, which is adequately suited for a small, trailerable or car top carryable craft, but would have limited practical usefulness in a larger cruising-size yacht intended to be left unattended at a dock or mooring for extended periods of time.
In accordance with the present invention, a novel and improved slot-forming foil mechanism is provided, suitable for installation on a cat-rigged or similar type of cruising or racing yacht and which is suitable to be left unattended on such yacht during extended periods of mooring or dockage. In accordance with another important aspect of the invention, a novel and improved slot-forming foil device is provided, which is of a two-part, asymmetrical construction, so as to provide an efficient aerodynamic shape in operation but which is aerodynamically inert when left unattended. More particularly the new slot-forming foil comprises a leading portion which is of symmetrical configuration, having a relatively bulbous leading edge portion and symmetrical, concavely contoured aft portions, terminating along a relatively fine trailing edge. Articulated along the full length of the trailing edge is an aft foil section, which is of symmetrical configuration, comprising a large radius arcuate back surface, and symmetrical, concavely contoured front surface portions joining along the center line of the section and defining its leading edge. The relatively sharp trailing edge of the forward section is joined to the leading edge of the after section along an axis of articulation. The flap-like aft section of the foil is provided with over-center means arranged to maintain it normally in one or the other of two operating positions. In either of its operating positions, it configures the articulated assembly to have an asymmetrical cross section comprising, on the "leeward" side a smooth, convex airfoil-like configuration and, on the "windward" side, a concave, slot-forming configuration. When tacking the vessel from one tack to the other, the flap-like foil section is pivoted to its opposite working position, so that the asymmetry of the slot-forming foil is reversed.
Significant improvements in windward performance of cat-rigged sailing vessels can be achieved with the new structure.
For a more complete understanding of the above and other features and advantages of the above invention, reference should be made to the following detailed description of a preferred embodiment and to the accompanying drawings.